It is now generally accepted that microbial/bacterial contamination or infection is a major factor influencing normal biological/physiological functions (such as healing or growth) and the rate of decomposition in many biological systems and processes. In wound healing, preventing wound infection is a vital aspect of wound care and recovery. Since all wounds are susceptible to infection, wound care best practise endeavours to take this into account. Typically wounds are cleaned to remove foreign debris that may harbour bacteria, and where tissues have suffered severe trauma, tissue repair is frequently assisted through suturing. In major surgical procedures such as hip replacement this involves repair of several tissue layers, followed by a sterile wound dressing of a type generally available. Typically a sterile wound dressing is applied to the skin surface to aid cleanliness and prevent infection.
Despite these precautions infection can become established through ingress of material during injury or inadvertently during various medical/surgical procedures. Furthermore problems of wound infection are not confined to deep wounds. Infection can transform relatively minor lesions into chronic wounds that increasingly pose major health care problems, particularly for the elderly, diabetic or infirm.
Over and above wound cleansing, various approaches have been adopted in an attempt to prevent the establishment of deep seated wound infections. Typically, antibiotics have been used systemically and locally or strong disinfecting chemicals have been used (in dental reconstruction for example) in an attempt to rid deep wounds of infectious bacteria. Unfortunately even the application of strong antimicrobial chemicals is frequently unsuccessful in preventing infection becoming established or recurring. In large part this may be due to the inability of the disinfecting agent to completely eradicate all problem bacteria. Additionally, as is well known, many bacteria are now resistant to antibiotics and their effectiveness becomes diluted over time.
There is therefore a need for more effective means to counteract bacterial infection and contamination. One approach has involved utilising bacteriophages (viruses that attack and destroy bacteria) and various groups have reported their successful application. Central problems associated with application of bacteriophages as a means of counteracting infection have been deriving an appropriate means of delivery whilst ensuring bacteriophages remain stable and viable long enough to exert their powerful antimicrobial effects.
Administration in liquid is not realistic or practical in many situations. The need is for a means of delivery that is generally suitable for application of bacteriophages as bactericidal agents and that has utility in many situations including wound care. Since bacteriophages are susceptible to degradation and desiccation, this should ideally also confer enhanced viability and stability.
Many conventional dressings employ a material which is designed to absorb excess fluid from within the wound; as such fluids are frequently rich in nutrients and are capable of supporting abundant bacterial growth. Since a surgical opening or the skin surface is rarely absolutely free of bacteria, the dressing or bandage material soon supports a growing bacterial population. Not only can the bacteria cause serious infection, but they may also release harmful toxins which lead to significant problems in terms of wound management. One solution is to routinely change the wound dressing or bandage, in order to prevent bacterial build-up, but this is not always desirable and/or practicable.
An alternative approach is to treat the dressing with an agent which is designed to limit microbial growth. However, many such agents can leach out of the dressing once in contact with wound exudates, so limiting the effectiveness of the dressing and indeed can be problematic with the active agent causing irritation or damage to surrounding tissue.
There is therefore a desire to provide antimicrobial dressings in which the antibacterial agent is not readily released from the dressing, or where the release of the agent would not be deleterious to the subject being treated.
WO 03/093462 discloses a method for immobilising viruses, such as bacteriophage, to a substrate, such that the viruses still retain infectivity.
It is amongst the objects of the present invention to provide a means to introduce bacteriophage into contaminated areas and environments so that the stability of bacteriophages is enhanced and their antimicrobial activity retained. This includes infected wounds, ranging from surface lesions to deep wound environments.
Separately, bacterial infections of plants can result in reduced germination, growth and/or yields. It is desirous to treat or prevent those infections, but approaches to doing so currently risk adversely affecting another factor influencing plant growth.
Another object of the invention is to address plant bacterial infections and provide plant material treated according to the invention and uses thereof.